The present invention relates to charging in a telecommunications system and more particularly, though not necessarily, to charging in a system in which a mobile terminal is connected through a mobile switching centre to make use of a service facilitated by an intelligent network.
As the number of exchanges in modern telecommunications networks has increased, there has been a tendency to centralize supplementary services (including call diversion, toll-free number access, premium rate number access, etc.) in certain specialized network nodes. Typically, these nodes are directly associated with only a relatively small number of exchanges. Callers requiring access to the supplementary services, but who are not directly connected to an exchange providing the service, are routed to a suitable exchange via their local exchange and possibly one or more transit exchanges. This technique of centralizing supplementary services is often referred to as xe2x80x9cIntelligent Networksxe2x80x9d.
In modern telecommunications networks, a node for detecting calls to an IN service is often referred to as a Service Switching Point (SSP). After detection of a call, an SSP communicates with a node having particular knowledge (e.g. a terminating B-number) of the IN service, termed the Service Control Point (SCP), to obtain information on how the connection is to be set up. Communication between the SSP and the SCP often makes use of (or is based upon) a standardized interface protocol known as ETSI CS1 (ETSI: ETS 300 374-1: see also ITU-T recommendations Q1218 1993 and 1995).
It will be appreciated that a caller (being allocated some A-number) will often be charged for making use of an IN service. For example, if a caller places a call to a premium rate number (e.g. a sports hotline) then he will be charged at some appropriate tariff. One function therefore of the SSP is to return to the SCP information which enables the SCP to determine if the accessed IN service is chargeable and, if so, the appropriate tariff. This information is normally provided to the SCP by the SSP following the termination of a call. This use of so-called xe2x80x9cflexible chargingxe2x80x9d may be applied more generally in telecommunications systems and is described in more detail in ICBS (Interconnection Charge Billing System) published by the Interconnection Charge Billing Forum, Tokyo, Japan.
There is currently a desire to be able to provide real time charging information to network operators and indeed to network users. This is particularly true in the case of mobile telephone users where much of the necessary technology is already in place, e.g. mobile telephones usually have a liquid crystal display on which real time charging information can be displayed.
The Japanese ARIB standard RCR STD-27x provides for charging information services known as Advice of Charge (AoC). The AoC service offers the possibility of informing a mobile terminal of the charge for a call originated by the terminal. Charge information is sent to the terminal upon release of the call. TTC JJ-70.10 also defines a so-called Inter-Network Charge Information Transmission (INCIT) functionality which provides for the exchange of certain call-related charging information between so-called visited and home networks. One further service which is available in some networks (although not yet standardized) is known as Charge Rate Information (ChRI). ChRI provides a charging notification element (containing charging information and a charge rate) to an originating terminal, either during call set-up or during the call itself, which allows the terminal to calculate the call cost.
In mobile telephone networks, telephone calls and associated signalling information are routed through a Mobile Switching Centre (MSC) which is analogous to a conventional telephone exchange. One of the functions of the MSC is to collect charging information on individual calls and to record that information for later billing. It is already possible to provide certain real time billing information to mobile subscribers based upon the data recorded at the MSC. However, this information relates only to basic call charges which can be calculated by the MSC based upon the location of the caller and of the called party. There exists no mechanism by which additional tariff information relating to an accessed IN service can be communicated to an originating MSC from an SSP/SCP node controlling the IN service. The same limitation applies to the general communication of tariff information across network boundaries, e.g. where operators have a cross-billing arrangement.
An object of certain aspects of the present invention is to overcome or at least mitigate the above noted disadvantage of existing telecommunications networks. In particular, it is an object to provide for the communication of tariff information from an external charge determination point to a mobile switching centre acting as charging point for a call originating mobile terminal, depending upon the classification of the call.
According to a first aspect of the present invention there is provided a method of determining charging information at a mobile switching centre of a mobile telecommunications network in respect of a call initiated by a mobile terminal registered with the network and terminating outside of the mobile switching centre, the method comprising, at the mobile switching centre:
classifying said call according to the associated A-number and/or the B-number as corresponding either to a call for which the mobile switching centre is to be the charge determination point or to a call for which an external node is to be the charge determination;
in the event that the call belongs to the latter class, receiving tariff information from the external charge determination point and calculating charge information on the basis of the received tariff information; and
in the event that the call belongs to the former class, disregarding any tariff information received from an external charge determination point and calculating charge information on the basis of the mobile telecommunications network""s own tariff information.
Preferably, in the event that the call belongs to the class for which the charge determination point is located outside of the mobile switching centre, a Request for Charge Information is sent by the mobile switching centre to the external charge determination point. More preferably, this request is sent as a flag contained in an Initial Address Message, transmitted as part of the call set-up phase.
Preferably, said tariff information comprises a Charge Information (CI) parameter, giving a call unit rate (or a set of call unit rates), and a Charge Information Type (CIT) parameter, indicating whether or not the CI parameter provides flexible charging information.
Preferably, the class of calls for which the charge determination point is located outside of the mobile switching centre, includes calls having A or B-numbers associated with Intelligent Network Services. More preferably, for such calls, the method comprises the steps of:
directing a request for access to the Intelligent Network service from the mobile switching centre to a service switching point of the system, together with a request for charging information, both of said requests being contained within an Initial Address Message sent as part of a call set-up routine;
in response to receipt of said Initial Address Message containing said request for charging information at the service switching point, sending a charging indicator request from the service switching point to a service control point having knowledge of the requested service;
in response to receipt of said charging indicator request at the service control point, sending a tariff indicator associated with the requested service from the service control point to the service switching point; and
determining at the service switching point, charging parameters on the basis of at least the received tariff indicator, and sending said charging parameters to said mobile switching centre.
Embodiments of the present invention enable IN service related charging information to be delivered from an IN service access node to a mobile switching centre. A mobile switching centre is therefore able to deliver accurate charging information to a calling mobile terminal, or to other components of the telecommunications system. The IN service access node may be located either in the mobile network or in a foreign network.
Preferably, said charging parameters are sent from the service switching point to the mobile switching centre during the call set-up routine. More preferably, said charging parameters are included in an address complete message (or an early address complete message). Preferably, the charging parameters determined at the service switching point are a charge information parameter and a charge information type parameter.
Preferably, communications between the service switching point and the service control point are based upon the ETSI CS1 protocol. Said charging indicator request is then sent from the service switching point to the service control point as a flexible charging indicator parameter contained in an InitialDP message. The tariff indicator may be returned in response as a parameter contained within the SendChargingInformation (SCI) message. More preferably, determination of said charging parameters at the service switching point is triggered by the subsequent receipt thereat of a message, sent from the service control point, containing a flexible charge request indicator.
Preferably, said charge information calculated by the mobile switching centre is employed either for AoC, ChRI, or INCIT service.
According to a second aspect of the present invention there is provided apparatus for determining charging information at a mobile switching centre of a mobile telecommunications network in respect of a call initiated by a mobile terminal-registered with the network and terminating outside of the mobile switching centre, the apparatus comprising, at the mobile switching centre:
classification means for classifying said call according to the associated A-number and/or the B-number as corresponding either to a call for which the mobile switching centre is to be the charge determination point or to a call for which the charge determination point is located outside of the mobile switching centre;
first processing means arranged, in the event that the call belongs to the latter class, to receive tariff information from the external charge determination point and calculating charge information on the basis of the received tariff information, or, in the event that the call belongs to the former class, to disregard any tariff information received from an external charge determination point and to calculate charge information on the basis of the mobile telecommunications network""s own tariff information.